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Sewage and sewerage of farm homes [1922]

Chapter 5: NATURE AND QUANTITY OF SEWAGE.
By George M. Warren
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About This Book

A practical manual outlines principles and procedures for safe disposal of household sewage on farms, defining sewage and sewerage, estimating volumes and composition, and identifying health hazards from pathogens and parasites. It explains biological decomposition and the importance of aeration, then provides step‑by‑step guidance on kitchen drains, cesspools, septic tanks, grease traps, distribution fields, and related construction details. Emphasis is placed on basing designs on local field data, proper installation, and continuous operation and maintenance to avoid odors, nuisance, and contamination of water supplies; illustrative plans and adaptable recommendations help readers select suitable treatments for varied site conditions.

NATURE AND QUANTITY OF SEWAGE.

Under average conditions a man discharges daily about 3½ ounces of moist feces and 40 ounces of urine, the total in a year approximating 992 pounds.[1] Feces consist largely of water and undigested or partially digested food; by weight it is 77.2 per cent water. 2 Urine is about 96.3 per cent water.[2]

[1] Practical Physiological Chemistry, by Philip B. Hawk, 1916, pp. 221, 359.

[2] Agriculture, by F. H. Storer, 1894, vol. 2, p. 70.

The excrements constitute but a small part of ordinary sewage. In addition to the excrements and the daily water consumption of perhaps 40 gallons per person are many substances entering into the economy of the household, such as grease, fats, milk, bits of food, meat, fruit, and vegetables, tea and coffee grounds, paper, etc. This complex product contains mineral, vegetable, and animal substances, both dissolved and undissolved. It contains dead organic matter and living organisms in the form of exceedingly minute vegetative cells (bacteria) and animal cells (protozoa). These low forms of life are the active agents in destroying dead organic matter.

The bacteria are numbered in billions and include many species, some useful and others harmful. They may be termed tiny scavengers, which under favorable conditions multiply with great rapidity, their useful work being the oxidizing and nitrifying of dissolved organic matter and the breaking down of complex organic solids to liquids and gases. Among the myriads of bacteria are many of a virulent nature. These at any time may include species which are the cause of well-known infections and parasitic diseases.